Prediction of phase separation in multi-component oxide glass for the fabrication of porous glass materials from waste slag

Thermodynamic analyses were performed to evaluate the composition ranges for metastable immiscibility including spinodal decomposition in multi-component silicate systems, where glass was regarded as a super-cooled liquid phase. Experimental studies on two-phase separation in glass were carried out, and the phase separation was observed in those silicate glasses corresponding to calculated metastable miscibility gaps. The authors also attempted the fabrication of porous glass using phase separation in oxide glasses containing B2O3. A multi-component borosilicate glass composition was prepared based on the silicate glass composition where spinodal decomposition had been confirmed. One of the glass phases formed by the spinodal decomposition in the boro-silicate glass was selectively removed by acid leaching and porous glass was successfully obtained.